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  1. leehuan

    Higher Level Integration Marathon & Questions

    Lol my bad. Idk why I decided to switch the cos out for a sin when posting
  2. leehuan

    Higher Level Integration Marathon & Questions

    \int_0^\infty \frac{\sin x}{x^2+1}dx
  3. leehuan

    Announcement from BOSTES/NESA - 2019 Syllabus Changes for Calculus courses

    Does anyone know if the year 11 content is also examinable for the new calculus syllabuses?
  4. leehuan

    Integration MC Question - North Sydney Boys 2017 Trial

    As correctly stated, A and B are good because they both equal to 0, soo they are ruled out. C fails because by taking the odd function f(x) = -x^3, we have \begin{align*} &\quad\int_{-a}^0 f(x)\,dx + \left| \int_0^a f(x)\,dx \right|\\ &= \int_{-a}^0 -x^3\,dx + \left| \int_0^a -x^3\,dx...
  5. leehuan

    HSC 2018-2019 MX2 Integration Marathon

    Re: HSC 2018 MX2 Integration Marathon $\noindent Take $f(x)$ to be any arbitrary odd function well defined for all $ -\frac\pi2 \leq x \leq \frac\pi2\\ $and let $ I = \int_{-\pi/2}^{\pi/2} \frac{\cos x}{e^{f(x)}+1}\,dx. $\noindent Considering the substitution $u=-x,\\ \begin{align*}I&=...
  6. leehuan

    HSC 2018-2019 MX2 Integration Marathon

    Re: HSC 2018 MX2 Integration Marathon \text{Let }I = \int_0^{\pi/6} \ln (\tan x + \sqrt{3} ) \,dx \begin{align*} I &= \int_0^{\pi/6} \ln \left( \frac{ \frac{1} {\sqrt3} - \tan x }{1 + \frac{\tan x}{\sqrt3} } + \sqrt{3} \right)dx\\ &= \int_0^{\pi/6 } \ln \left( \frac{4}{\sqrt3 + \tan x}...
  7. leehuan

    Announcement from BOSTES/NESA - 2019 Syllabus Changes for Calculus courses

    I interpreted that as something like $Find the area between the curves $y=x^2$ and $y=1-x^2
  8. leehuan

    Announcement from BOSTES/NESA - 2019 Syllabus Changes for Calculus courses

    Looks like it says "area under curve" which implied just x-axis to me? Unless "under" actually includes "to the left of" as well
  9. leehuan

    Announcement from BOSTES/NESA - 2019 Syllabus Changes for Calculus courses

    This is a bit dumb but are areas w.r.t. the y-axis still in the maths advanced syllabus? I can't find it. (Can find appropriate volumes in ext 1)
  10. leehuan

    Higher Level Integration Marathon & Questions

    \int_0^{10} x^{\lim_{n\to \infty} f^n(x)}\,dx \text{ for }f(x) = \frac12 \left( x + \frac2x\right) \text{where }f^n(x) = \underbrace{f \cdots f}_{n\text{-times}}(x) Shouldn't be hard assuming I didn't mess up typing the question.
  11. leehuan

    Higher Level Integration Marathon & Questions

    @Paradoxica I think I finally figured what it should've been. \int_1^e x \sqrt[6]{x^{-1} \sqrt[20]{x \sqrt[42]{x^{-1} \dots}}}\,dx Well, hopefully.
  12. leehuan

    MATH2601 Higher Linear Algebra

    I'd recommend InteGrand's rearrangement. But it's still fairly easy just using what they give you. \text{Closure condition: Let }x,y\in C_g\text{, so we have} \\ \begin{align*} gx &= xg \\ gy &= yg \end{align*} \noindent\text{Then, with the aid of the associative rule,} \\ \begin{align*} g(xy)...
  13. leehuan

    MATH2701 Abstract Algebra/Fundamental Analysis

    This was in the final exam and I never figured it out. \text{Let }f:\mathbb{R}\to \mathbb{R}\text{ be a convex function. Prove that for any }x,y,z\in \mathbb{R}, \frac{ f(x)+f(y)+f(z) }3 + f \left( \frac{x+y+z}3 \right) \ge \frac{2}{3} \left[ f \left( \frac{x+y}{2} \right) + f \left(...
  14. leehuan

    HSC 2018-2019 MX2 Integration Marathon

    Re: HSC 2018 MX2 Integration Marathon Which isn't even 4U. Savage,
  15. leehuan

    HSC 2018-2019 MX2 Integration Marathon

    Re: HSC 2018 MX2 Integration Marathon That being said is there a way of doing it using only 4U methods
  16. leehuan

    I forgot the clever way of doing these integrals...

    \int \frac{\sin^2 x - 4\sin x \cos x + 3\cos^2 x}{\sin x +\cos x}dx
  17. leehuan

    Announcement from BOSTES/NESA - 2019 Syllabus Changes for Calculus courses

    Has there been any word from MANSW regarding the new syllabuses?
  18. leehuan

    Higher Level Integration Marathon & Questions

    \text{The substitution }x=\exp (-u)\text{ turns the first integral into }\int_0^\infty u^n \log u \exp (-u)\,du \text{Call it }I_n.\text{ From IBP,}\\ \begin{align*}I_n&= -e^{-u}u^n \log u \Big |_0^\infty + \int_0^\infty e^{-u}u^{n-1}\left(1 + n \log u\right)\,du\\ &= J_{n-1}+ n...
  19. leehuan

    Higher Level Integration Marathon & Questions

    \int_0^\pi \ln(1+2a\cos x + a^2)\,dx\text{ splitting into appropriate cases} (Not sure if already asked)
  20. leehuan

    Higher Level Integration Marathon & Questions

    At least quick partial fractions is possible this time round lol u^2 = \tanh x \implies 2u\,du = \text{sech}^2 x\,dx = (1-\tanh^2 x)\,dx\quad (u\ge 0) \begin{align*} I & = \int \sqrt{ \tanh x} \, dx\\ &= \int \frac{2u^2}{1-u^4} \, du\\ &= \int \frac{2u^2}{(1-u^2)(1+u^2)}\,du\\ &=...
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